The present invention relates to a novel method of dry cleaning of fabric materials and a dry cleaning solvent used therefor. More particularly, the invention relates to a dry cleaning method of fabric materials having advantages of, besides the high cleansing effect exhibited to an oily or greasy dirt deposited on the fabric material and pleasant touch feeling of the fabric material finiashed by the dry cleaning method, absence of unpleasant smell therefrom, little problems against environmental pollution possibly leading to destruction of the ozone layer in the aerosphere and safety against workers"" health by virtue of the use of a unique dry cleaning solvent which has never been employed for this purpose of dry cleaning.
Needless to explain, dry cleaning is a process for cleaning a fabric material such as clothes in which the fabric material is immersed in or soaked with a non-aqueous organic solvent capable of dissolving oily or greasy dirt materials deposited on the fabric material so as to dissolve the dirt material out of the fabric material into the solvent followed by removal of the solvent from the cleaned fabric material and drying thereof.
A great variety of organic solvents have been proposed as the dry cleaning solvent and are actually employed for the purpose, of which the solvents currently under wide applications include halogenated hydrocarbon solvents, such as chlorofluorinated hydrocarbons and chlorinated hydrocarbons such as perchloroethylene, trichloroethylene and trichloroethane, and petroleum-based hydrocarbon solvents which are mainly paraffinic or naphthenic.
While advantageous in respects of non-inflammability and rapid drying, the above mentioned halogenated hydrocarbon solvents as a dry cleaning solvent have serious problems because vapors of such a halogenated hydrocarbon solvent emitted to the atmosphere are suspected to be liable for destruction of the ozone layer in the aerosphere in addition to the problem against public and workers"" health due to contamination of the underground wate by discarded dry cleaning solvents and environmental pollution by the solvent vapor.
Accordingly, it is now a world-wide trend that use of halogenated hydrocarbon solvents is going to be banned not only as a dry cleaning solvent but also in any other applications. Petroleum-based hydrocarbon solvents are also noxious as an environmental pollutant against workers"" health. For example, regulations in many countries prescribe the maximum permissible concentration of vapors of petroleum-based hydrocarbon solvents in the working environment at a very low level in order to ensure workers"" health against toxication by the solvents. Among various proposals to solve this problem, Japanese Patent No. 1502875 proposes use of a cyclic organopolysiloxane oligomer or a mixture thereof with a petroleum-based hydrocarbon solvent as a dry cleaning solvent. Japanese Patent Kokai 6-327888 further discloses a method of dry cleaning by using a volatilizable organopolysiloxane having a straightly linear molecular structure as the dry cleaning solvent.
The above mentioned cyclic organopolysiloxane oligomer, however, has a disadvantage, when used as a dry cleaning solvent, that the cyclic organopolysiloxane oligomer is susceptible to ring-opening polymerization by the catalytic activity of the acidic or basic compound contained in the contaminant dirt material deposited on the fabric material for cleaning to produce a non-volatile organopolysiloxane of an increased degree of polymerization which in turn is deposited on the fabric material sometimes adversely affecting the touch feeling of the finished fabric material.
Japanese Patent Kokai 11-214587 teaches that organopolysiloxane oligomers are useful as a washing solvent of articles of a metal, ceramic, glass and plastic as well as semiconductor materials. It is unclear there, however, whether or not the organopolysiloxane oligomer be effective as a dry cleaning solvent for fabric materials or, in particular, clothes.
In view of the above described problems in the prior art method of dry cleaning, the present invention has an object to provide a novel method for dry cleaning of a fabric material by using a unique volatilizable organopolysiloxane compound as the dry cleaning solvent having advantages, in addition to the excellent cleansing effect on not only oily or greasy dirt materials but also some water-soluble dirt materials and very pleasant touch feeling of the fabric material finished by the method, that the dry cleaning solvent is not toxic against human body to ensure safety to the public and workers"" health and that the solvent is not liable for the destruction of the ozone layer in the aerosphere due to emission of the vapor thereof to the atmosphere. The invention also has an object to provide a dry cleaning solvent used in the dry cleaning method.
Thus, the method of the present invention for dry cleaning of a fabric material comprises the steps of:
(a) immersing the fabric material in or soaking the fabric material with a dry cleaning solvent which is a tris(trimethylsiloxy) silane compound represented by the general formula
RSi(xe2x80x94Oxe2x80x94SiMe3)3,xe2x80x83xe2x80x83(I)
xe2x80x83In which Me is a methyl group and R is a monovalent hydrocarbon group having 1 to 6 carbon atoms, or a mixture thereof with a petroleum-based hydrocarbon solvent so as to dissolve dirt materials on the fabric material into the solvent;
(b) removing the dry cleaning solvent containing the dirt materials dissolved therein from the fabric material by solid-liquid separation; and
(c) drying the fabric material wet with the dry cleaning solvent.
The invention also provides a dry cleaning solvent used in the above defined method of dry cleaning which comprises:, as a uniform mixture:
(A) at least 30% by weight of the tris(trimethylsiloxy) silane compound represented by the above given general formula (I); and
(B) a petroleum-based hydrocarbon solvent in an amount not exceeding 70% by weight.